Chemotherapy is still an important option for the treatment of various types of cancers. The chemotherapeutic drugs preferentially target tumor cells and act by impairing mytosis by various mechanisms including damaging DNA and inhibition of the cellular machinery involved in cell division.
Continuous research work for new cytotoxic agents with unique mechanisms of action is carried worldwide to develop novel potent and selective anti-cancer agents.
One of the oldest and most effective strategies for developing new chemotherapeutic drugs is the isolation and evaluation of chemicals present in natural form. The importance of natural products for drug discovery has been impressive and there are a large number of active drugs used in cancer therapy which are based on natural products.
Pyarrocarbazoles, Phenothiazidines, nitrogen containing heterocyclic compounds of natural origin are known to possess cytotoxic activity. Norsesquiterpenes and sesquiterpenesare a class of naturally occurring molecules that have demonstrated therapeutic potential in decreasing the progression of cancer. These alkaloids are isolated from both plant and marine life and are modulated in the art for treatment of cancer.
Kai-Shun Bi et al. in an article titled “A novel norsesquiterpene alkaloid from the mushroom-forming fungus Flammulinavelutipes” in Chinese Chemical Letters 2013, 24, 57-58 reports the isolation of novel tricyclic compound (1) from the solid culture of mushroom-forming fungus Flammulinavelutipes fermented on rice. According to this article the compound showed cytotoxicity against KB cells in vitro with an IC50 value of 16.6 μmol/L.

In addition to this in literature related compounds are also known for PARP-1 (poly(ADP-ribose) polymerase-1) inhibition. M. Tao et al. in an article titled “Synthesis and structure-activity relationships of novel poly(ADP-ribose) polymerase-1 inhibitors” reported compound 2 as PARP-I inhibitor in Bioorg. Med. Chem. Lett. 2006, 16, 938-942. Also several related compounds of structure 2 are claimed in a patent publication, US 2006/0276497 A1.
Article titled ‘Serendipitous Discovery of a Prodrug of a PARP-1 Inhibitor’ by Derek Dunn, Jean Husten et al published in Chem Biol Drug Des 2013; 82: 348-350 discloses a series of N-alkyl analogs of compound 1 and compound 2 having anticancer activity;
wherein,X═CH2NH2. 
Although, new chemotherapeutic agents are continuously developed, many of them have not been therapeutically useful due to low tumor selectivity and harsh side effects.
Thus there remains a need in the current scenario to provide novel anti-cancer compounds which have potent and selective activity towards tumor cells.
The present invention is thus directed to meet the above requirements by providing novel heterocyclic compounds from sesquiterpene class of alkaloids as potent anti-cancer agents.